An existing four-way reversing valve is mainly comprised of an electromagnetic coil, a pilot valve and a main valve. During the control, the reversing of the main valve is achieved through the cooperation of the electromagnetic coil and the pilot valve to switch the circulating direction of the refrigerant, such that a heat pump air conditioner is switched between refrigeration state and heating state, thus realizing two functions with one machine, i.e., refrigerating in summer and heating in winter.
The main valve of the existing four-way reversing valve has three ports: a port S in communication with a suction port of a compressor, a port E in communication with an indoor heat exchanger and a port C in communication with an outdoor heat exchanger. Two end covers are respectively tightly connected with two side end portions of a cylindrical valve body to form a closed inner valve chamber of the main valve. The inner valve chamber of main valve is divided into three chambers, i.e., left, middle and right chambers by two pistons, in which the left chamber is communicated with a port e of a pilot valve and the right chamber is communicated with a port c of the pilot valve. In this way, under the control of the pilot valve, a slider inside the main valve is displaced along with the pistons, achieving the switch between two operating states of refrigeration state and heating state. In refrigerating position, the slider is slid to the left, the port E is communicated with the port S and the port D is communicated with the port C, and the left piston and an inward projecting portion of the left end cover abut against each other in this condition. In heating position, the slider is slid to the right, the port S is communicated with the port C and the port D is communicated with the port E, and the right piston and an inward projecting portion of the right end cover abut against each other in this condition.
It is known from the above described analysis of the operating principle, the requirement for precision in assembly and welding process between the two end covers and the valve body is relatively high. Reference is made to FIG. 1, which shows the position relationship between an end cover 1a and a valve body 2a of a prior art four-way reversing valve. After inserted into the inner chambers at two sides of the valve body 2a, the end valve 1a is fixedly connected thereto by argon welding. This fitting relationship ensures the fulfilling of the requirement for the position tolerance of the inward projected portion of the end cover by the cylindrical outer periphery surface of the end cover 1a and the inner wall of the valve body 2a abutting against each other.
Reference is also made to FIG. 2, which is an enlarged view of portion I in FIG. 1. However, the existing valve bodies are made of stainless steel sheet by drawing, and most finished valve bodies present cylindricity error; that is, there is phenomenon that one end of the valve body has a larger inner diameter and other end has a smaller inner diameter. Therefore, there is a problem that the fitting between the end cover and the valve body has a larger gap at one end while being tight at the other end. Then, in the practical assembly, the valve body is usually expanded after the end cover is pressed into the smaller diameter end of the valve body, so that a clearance fit is formed between the rear portion of the end cover and the valve body. As the fit clearance between the end cover and the larger diameter end of valve body is relatively large, the position precision and welding quality therebetween may be thus affected.
For this reason, optimization design is intended to be made for the existing end cover to ensure the assembly and welding precision between the end cover and the valve body through improvement of structural form.